The assessment of high recharge areas using DO indicators and recharge potential analysis: a case study of Taiwan’s Pingtung plain

Identifying high groundwater recharge areas is important for the conservation of groundwater quality and quantity. A common practice used by previous studies is to estimate groundwater recharge potential (GRP) using recharge potential analysis (RPA) under different environments. These studies use the estimated GRP to identify the high potential groundwater recharge sites. However, the RPA parameters are subjectively defined for these previous studies. To remove the supposition, this study proposes a systematic approach that defines the RPA parameter values based on the theory of parameter identification. This study uses dissolved oxygen (DO) indicators to calibrate the RPA parameters. This calibration improves the correlation coefficient between the DO indicators and computed GRP values from 0.63 to 0.87. By comparing the initial values, these results indicate that the estimated RPA parameters better represent the field infiltration characteristic. This result also indicates that defining the RPA parameter values based on DO indicators is necessary and important for accuracy. These calibrated parameters are used to estimate the GRP distribution of Taiwan’s Pingtung Plain. The GRP values are delineated into five levels. High and excellent GRP areas are defined as high recharge areas, which compose about 26.74 % of the study area. Based on the proposed method, the estimated GRP distribution can accurately represent the study area’s field recharge characteristics. These study results can be a good reference for groundwater recharge analyses, specifically if well data is limited or difficult to obtain.     

Pulsar simulations for the Fermi Large Area Telescope

Pulsars are among the prime targets for the Large Area Telescope (LAT) aboard the recently launched Fermi observatory. The LAT will study the gamma-ray Universe between 20 MeV and 300 GeV with unprecedented detail. Increasing numbers of gamma-ray pulsars are being firmly identified, yet their emission mechanisms are far from being understood. To better investigate and exploit the LAT capabilities for pulsar science, a set of new detailed pulsar simulation tools have been developed within the LAT collaboration. The structure of the pulsar simulator package (PulsarSpectrum) is presented here. Starting from photon distributions in energy and phase obtained from theoretical calculations or phenomenological considerations, gamma-rays are generated and their arrival times at the spacecraft are determined by taking into account effects such as barycentric effects and timing noise. Pulsars in binary systems also can be simulated given orbital parameters. We present how simulations can be used for generating a realistic set of gamma-rays as observed by the LAT, focusing on some case studies that show the performance of the LAT for pulsar observations.     

A field investigation of the sediment transport characteristics of a high sediment load intermittent river in Taiwan

Most rivers in Taiwan are intermittent rivers with relatively steep slopes and carry rapid sediment‐laden flows during typhoon or monsoon seasons. A series of field experiments was conducted to collect suspended load data at the Tzu‐Chiang Bridge hydrological station of the lower Cho‐Shui River, which is a major river with the highest sediment yield in Taiwan. The river reach was aggrading with a high aspect ratio during the 1980s. Because of sand mining and extreme floods, it was incised and has had a relatively narrow main channel in recent years. The experimental results indicated that typical sediment transport equations can correctly predict the bed material load for low or medium sediment transport rates (e.g. less than about 1000 tons/day‐m). However, these equations far underestimate the bed material load for high sediment transport rates. The effects of cross‐sectional geometry change (i.e. river incision) and earthquakes on the sediment load were investigated in this study. An empirical sediment transport equation with consideration of the aspect ratio was also derived using the field data collected before and after river incision. Copyright © 2012 John Wiley & Sons, Ltd.     

Particulate matter and gaseous pollutants during a tropical storm and air pollution episode in Southern Taiwan

Gaseous pollutants and PM_2.5 aerosol particles were investigated during a tropical storm and an air pollution episode in southern Taiwan. Field sampling and chemical analysis of particulate matter and gaseous pollutants were conducted in Daliao and Tzouying in the Kaohsiung area, using a denuder-filter pack system during the period of 22 October to 3 November 2004. Sulfate, nitrate and ammonium were the major ionic species in the PM_2.5, accounting for 46 and 39% of the PM_2.5 for Daliao and Tzouying, respectively. Higher PM_2.5, Cl^?, NO₃^? and NH₄⁺, HNO₂ and NH₃ concentrations were found at night in both stations, whereas higher HNO₃ was found during the day. In general, higher PM_2.5, HCl, NH₃, SO₂, Cl^?, NO₃^?, SO₄^2? and NH₄⁺ concentrations were found in Daliao. The synoptic weather during the experiment was first influenced by Typhoon NOCK-TEN, which resulted in the pollutant concentrations decreasing by about two-thirds. After the tropical thunderstorm system passed, the ambient air quality returned to the previous condition in 12 to 24 h. When there was a strong subsidence accompanied by a high-pressure system, a more stable environment with lower wind speed and mixing height resulted in higher PM_2.5, as well as HNO₂, NH₃, SO₄^2?, Cl^?, NO₃^?, NH₄⁺ and K⁺ concentrations during the episode days. The rainfall is mainly a scavenger of air pollutants in this study, and the stable atmospheric system and the high emission loading are the major reasons for high air pollutant concentrations.     

Correlating recurrent radon precursors with local earthquake magnitude and crust strain near the Chihshang fault of eastern Taiwan

The active Chihshang fault in the southern segment of longitudinal valley of eastern Taiwan is part of the suture boundary between the Eurasia plate and the Philippine Sea plate. Radon anomalies in groundwater were recorded prior to three major earthquakes—(1) 2003 M _w = 6.8 Chengkung, (2) 2006 M _w = 6.1 Taitung, and (3) 2008 M _w = 5.4 Antung. The epicenters were located 24, 52, and 13 km, respectively, from the radon-monitoring well (D1) in the Antung hot spring about 3 km southeast of the Chihshang fault. Prior to the three major earthquakes, radon decreased from background levels of 787 ± 42, 762 ± 57, and 700 ± 57 pCi/L to minima of 326 ± 9, 371 ± 9, and 480 ± 43 pCi/L, respectively. Based on the radon volatilization model and the rock dilatancy model, this paper correlates the observed radon minima with local earthquake magnitude and crust strain. The correlation is a useful means of forecasting local disastrous earthquakes in the southern segment of longitudinal valley of eastern Taiwan.     

A Practical Approach to Evaluating Natural Attenuation of Contaminants in Ground Water

The extent of natural attenuation is an important consideration in determining the most appropriate corrective action at sites where ground water quality has been impacted by releases of petroleum hydrocarbons or other chemicals. The objective of this study was to develop a practical approach that would evaluate natural attenuation based on easily obtained field data and field tested indicators of natural attenuation. The primary indicators that can he used to evaluate natural attenuation include plume characteristics and dissolved oxygen levels in ground water. Case studies of actual field sites show that plumes migrate more slowly than expected, reach a steady state, and decrease in extent and concentration when natural attenuation is occurring. Background dissolved oxygen levels greater than 1 to 2 mg/L and an inverse correlation between dissolved oxygen and contaminant levels have been identified through laboratory and field studies as key indicators of aerobic biodegradation. an important attenuation mechanism. Secondary indicators such as geochemical data, and more intensive methods such as contaminant mass balances, laboratory microcosm studies, and detailed ground water modeling can demonstrate natural attenuation as well. The recommended approach for evaluating natural attenuation is to design site assessment activities so that required data such as dissolved oxygen levels and historical plume flow path concentrations are obtained. With the necessary data, the primary indicators should be applied to evaluate natural attenuation. II the initial evaluation suggests that natural attenuation is a viable corrective action alternative, then a monitoring plan should be implemented to verify the extent of natural attenuation.     

Assessing climate change impacts on California hydropower generation and ancillary services provision

Climate change is already affecting species and their distributions. Distributional range changes have occurred and are projected to intensify for many widespread plants and animals, creating associated risks to many ecosystems. Here, we estimate the climate change-related risks to the species in globally significant biodiversity conservation areas over a range of climate scenarios, assessing their value as climate refugia. In particular, we quantify the aggregated benefit of countries’ emission reduction pledges (Intended Nationally Determined Contributions and Nationally Determined Contributions under the Paris Agreement), and also of further constraining global warming to 2 °C above pre-industrial levels, against an unmitigated scenario of 4.5 °C warming. We also quantify the contribution that can be made by using smart spatial conservation planning to facilitate some levels of autonomous (i.e. natural) adaptation to climate change by dispersal. We find that without mitigation, on average 33% of each conservation area can act as climate refugium (or 18% if species are unable to disperse), whereas if warming is constrained to 2 °C, the average area of climate refuges doubles to 67% of each conservation area (or, without dispersal, more than doubles to 56% of each area). If the country pledges are fulfilled, an intermediate estimate of 47–52% (or 31–38%, without dispersal) is obtained. We conclude that the Nationally Determined Contributions alone have important but limited benefits for biodiversity conservation, with larger benefits accruing if warming is constrained to 2 °C. Greater benefits would result if warming was constrained to well below 2 °C as set out in the Paris Agreement.     

On the antenna beam shape reconstruction using planet transit

The calibration of the in-flight antenna beam shape and possible beamdegradation is one of the most crucial tasks for the upcoming Planck mission. We examine several effects which could significantly influence the in-flight main beam calibration using planet transit: the problems of the variability of the Jupiter’s flux, the antenna temperature and passing of the planets through the main beam. We estimate these effects on the antenna beam shape calibration and calculate the limits on the main beam and far sidelobe measurements, using observations of Jupiter and Saturn. We also discuss possible effects of degradation of the mirror surfaces and specify corresponding parameters which can help us to determine these effects.     

Integrating hydrometeorological information for rainfall‐runoff modelling by artificial neural networks

The major purpose of this study is to effectively construct artificial neural networks‐based multistep ahead flood forecasting by using hydrometeorological and numerical weather prediction (NWP) information. To achieve this goal, we first compare three mean areal precipitation forecasts: radar/NWP multisource‐derived forecasts (P_r), NWP precipitation forecasts (P_n), and improved precipitation forecasts (P_m) by merging P_r and P_n. The analysis shows that the accuracy of P_m is higher than that of P_r and P_n. The analysis also indicates that the NWP precipitation forecasts do provide relative effectiveness to the merging procedure, particularly for forecast lead time of 4–6 h. In sum, the merged products performed well and captured the main tendency of rainfall pattern. Subsequently, a recurrent neural network (RNN)‐based multistep ahead flood forecasting techniques is produced by feeding in the merged precipitation. The evaluation of 1–6‐h flood forecasting schemes strongly shows that the proposed hydrological model provides accurate and stable flood forecasts in comparison with a conventional case, and significantly improves the peak flow forecasts and the time‐lag problem. An important finding is the hydrologic model responses which do not seem to be sensitive to precipitation predictions in lead times of 1–3 h, whereas the runoff forecasts are highly dependent on predicted precipitation information for longer lead times (4–6 h). Overall, the results demonstrate that accurate and consistent multistep ahead flood forecasting can be obtained by integrating predicted precipitation information into ANNs modelling. Copyright © 2009 John Wiley & Sons, Ltd.